1. Technical Field
The present invention relates to an optical disk drive which records information on an optical disk and, more particularly, to a technique for determining a recording strategy used at the time of recording operation.
2. Related Art
A hitherto-available method—by means of which an optical disk drive capable of recording data on a DVD-RW, or the like, stores data in an optical disk—is one for controlling a pulse width or a pulse interval of a recording pulse in accordance with conditions for a recording pulse which are called a “recording strategy.” Recording quality is enhanced by use of this method.
In relation to the recording strategy, recommended values are usually determined by a disk manufacturer, or the like. Moreover, the recording strategy is previously recorded as a recommended recording strategy in a predetermined area on the optical disk. However, characteristics of an optical pickup vary from one optical disk drive to another. For this reason, it may be the case where some of the optical disk drives fail to acquire sufficient recording quality when recording is performed by use of a previously-determined recording strategy.
Accordingly, in connection with known optical disks previously expected to be used, there is a case where unique optimum recording strategies of respective optical disk drives have been determined previously and where the thus-determined optimum recording strategies are stored in nonvolatile memory, such as flash ROM provided in an optical disk drive. Use of such an individual recording strategy enables greater enhancement of recording quality when compared with a case where recording is performed by use of the recommended recording strategy. However, because of alterations in specifications of a known disk or variations in manufacture, it may be the case where sufficient recording quality is not acquired even when data are recorded by use of the optimum recording strategy previously held in the optical disk drive.
Meanwhile, in the case of an unknown optical disk whose optimum recording strategy has not been in advance, there may be the case where an intermediate recording strategy for use with an unknown optical disk is stored in nonvolatile memory or where a recommended recording strategy recorded in a predetermined area on the optical disk and determined by a disk manufacturer, or the like, is used in unmodified form. However, an individual difference exists in each of disk drives with regard to the wavelength of a laser diode of an optical pickup (OPU) and an angle of inclination of an optical axis with respect to a disk plane. Therefore, there may arise a case where use of such a recording strategy results in a failure to acquire sufficient recording quality.
Accordingly, methods described in JP 2003-59047 A and JP 2005-322312 A have been proposed as a method for determining a recording strategy for an unknown optical disk.
Under an optical disk recording method described in JP 2003-59047 A, an unknown optical disk whose recording strategy is not stored in memory or an optical disk whose recording strategy stored in memory fails to allow acquisition of superior recording quality is subjected to test recording, while recording power is being changed, by use of all of recording strategies stored in memory or a plurality of appropriately-adopted recording strategies. Thus, a recording strategy which allows acquisition of relatively-high signal quality is selected and used for actual recording.
Under an optical disk recording method described in JP 2005-322312 A, when an optical disk whose optimum recording strategy is not identified is subjected to recording, a recording strategy used at the time of recording is determined from a recommended recording strategy recorded in a predetermined are of an optical disk and a characteristic of the optical pickup of the optical disk drive, and the optical disk is subjected to recording in accordance with the thus-determined recording strategy.
Specifically, JP 2003-59047 A describes processing for determining a recording strategy used at the time of recording by means of subjecting an unknown optical disk to a plurality of test recording operations by use of a plurality of recording strategies. JP 2005-322312 A describes processing for determining a recording strategy from a recommended recording strategy and a characteristic of the optical pickup of the optical disk drive. However, these processing operations are more complicated than processing for determining a recording strategy of a known optical disk, and there is a risk of consumption of a long period of time before performance of actual recording.